Demyelinating and Autoimmune Disease

Abstract

A number of neurological disorders appear to have primary demyelination as their common pathological basis. In these disorders the primary pathological event appears to be a local breaking down of myelin in the central and/or peripheral nervous system, with a relative preservation of axis cylinders formerly encased in the affected myelin. Multiple sclerosis is the most common of the primary demyelinating diseases. Despite a great deal of research it is probably fair to say that there is no generally accepted view as to the aetiology of multiple sclerosis, as to how the episodes of demyelination are precipitated, and as to what determines their location in the central nervous system. The main hypotheses now in vogue are that multiple sclerosis is an autoimmune disorder, or is due to ‘slow virus’ infection. The aetiologies of neuromyelitis optica and Schilder’s sudanophil diffuse sclerosis also remain obscure, though one form of the latter, associated with adrenal insufficiency, appears to be inherited as a sex-linked recessive. The animal model of experimental allergic encephalitis provides some basis for understanding the pathogenesis of the primary demyelinating neuritides and radiculopathies (Guillain-Barre syndrome), and the myelinoclastic encephalomyelopathies. The latter may be idiopathic, or para-infectious (associated commonly with measles, varicella, smallpox vaccination). Experimentally, analogous neuropathological appearances of areas of perivenous demyelination can be produced by immunising animals against their own peripheral or central myelin. It is thought that trivial or more major infection, or immunisation, can sometimes make a person ‘allergic’ to his own myelin.